The present invention relates to apparatus for the avoidance of overspeeding of a combustion engine, especially an internal combustion engine for an automotive vehicle. More particularly, the invention relates to such an apparatus which utilizes a disengageable clutch which is connected in a drive train for the drive of an automotive vehicle, such as in conjunction with the shifting transmission.
It is known that considerable damage can result to an engine when it is operated at speeds above its highest desirable speed or rotational speed, especially if so operated for a long period of time. In certain circumstances with automotive vehicle engines, such damage can affect the safety of the vehicle, the vehicle passengers, and also other traffic vehicles. Since such overspeeding results often only from inattentiveness, the invention is directed to the problem of creating an arrangement which automatically undertakes the supervision of the running speed and the automatic initiation of appropriate counter-measures. Such an arrangement should preferably be simply constructable and operationally safe.
According to the invention, these above-noted problems are solved by providing effective adjustment apparatus for the clutch so as to automatically disengage the clutch upon the reaching of a predetermined speed of the engine. The selected predetermined speed for the apparatus is advantageously chosen such that it is slightly under the permissible highest operational speed of the engine, so that, considering the inertia of the apparatus, a proper disengagement of the gears is possible. According to preferred embodiments of the invention, the control is such that the clutch can be mechanical, pneumatic, hydraulic or electric. The control can also be specifically directly for the clutch itself, as well as also for its existent activating part or linkage.
The invention also contemplates the general idea of separating or interrupting the drive train from the engine or motor to the driving wheels automatically, in dependence on the reaching of a predetermined critical engine speed. The disengaging impulse for the drive train can, in practical appropriate embodiments, be controlled by engine speed dependent frequencies; e.g., in dependence upon the generator or a mechanical control signal. It is also contemplated within the framework of the invention for the selected predetermined engine speed to be made to be adjustable so as to accommodate certain desired different driving styles (sport driving or maximum economy driving, for example). It is also contemplated to coordinate different predetermined engine speeds for individual gears in order to prevent excessive speed operation in the lower gears during acceleration.
According to a further development of the inventive concept, the arrangement can be so constructed that the arrangement for activating the clutch is also effective to regulate the engine in the sense of an adjustment for no-load running. In this way, it is established in each case that the engine will not by chance run away (excessive overspeeding) if, for whatever reasons, the driver keeps his foot on the throttle pedal upon activation of the clutch disengaging apparatus of the invention.
Further, there are driving situations where, for safety reasons, an overrunning or overspeeding of the engine beyond the predetermined highest desired operational speed is necessary. For example, if the brakes fail, such intentional overspeeding may be required for braking purposes. For this reason, the present invention further proposes that an emergency switch or the like be provided for the intentional shut-off or cut-out of the control apparatus for the disengagement of the clutch.
Modern vehicle clutches are frequently hydraulically operated in such a manner that a first piston-cylinder arrangement directly controls the engagement and disengagement of the clutch, with a second piston-cylinder arrangement being operated by a clutch pedal in such a manner as to selectively apply pressure to the first cylinder arrangement. With such a clutch arrangement, the invention proposes that the second or activating cylinder connected with the clutch pedal, on the back side thereof, is pressurizable by a pressure medium controlled by a solenoid valve with the activating circuit for such solenoid valve being controlled in response to an engine speed responsive switch (tachometer switch) set to close the activating circuit when the engine exceeds a predetermined set speed.
The engine tachometer switch, in accordance with a first embodiment of the invention, operates so as to control the reengagement of the clutch after the slowing down of the engine below a selected speed, with consequent advantages of automatic continuous operation of the vehicle system. However, in accordance with a second preferred embodiment of the invention, the clutch is maintained in a disengaged position until further intentional activation of same by the vehicle driver. In this last-mentioned arrangement, the control of a relay for the solenoid valve is to be equipped with a stopping circuit, including a switch for controlling deactuation of the solenoid valve.
According to a further preferred embodiment of the invention, it is further proposed that the pressure medium supplied to the activating cylinder for controlling the clutch is also connected to a further pressure medium cylinder, the piston of which further cylinder is operable to move an engine speed control rod in a direction corresponding to a decreasing engine load upon the pressurization of the mentioned cylinders. In this way it will be in each case assured that the engine is returned to a no-load running speed situation irrespective of the position that the driver maintains his foot on the accelerator pedal.